More descriptive parameter names (Unity-Technologies#215)

* Add descriptive parameter names for lerp.

* Better names for unlerp.

* Descriptive names for mad() and remap().

* Descriptive names for clamp.

* Descriptive names for smoothstep.

* Descriptive names for select.

* Descriptive step.

* Descriptive refract.

* Descriptive project.

* Changelog update.

Author: unpacklo

src/CHANGELOG.md

@@ -15,6 +15,7 @@
 ### Changed
 * `asfloat(uint)`, `asuint(float)`, `asint(float)` and other related methods are now faster in mono without Burst. Other methods which use these will see a performance improvement.
 * Modified `quaternion.nlerp` to be branchless.
+* More descriptive parameter names for many methods in `math` class.
 ### Deprecated
 ### Removed
 ### Fixed